This invention relates to a telephone conference bridge system.
A conference bridge is a device which allows several telephone lines to be bridged together to establish a telephone conference with negligible effect on transmission. Each line connection to the bridge is known as a port.
Telephone conferencing systems are known in the art. For example, Canadian Pat. No. 1,093,194 of Fenton et al, issued Jan. 6, 1981, discloses a communication system call conference control arrangement using a stored program control. The system uses a microprocessor and is capable of conference calls and provides various status indications by means of LED's. The stations use a telephone having a plurality of special buttons in addition to the normal dialing buttons. In the patent such a telephone is termed a multibutton electronic telephone (MET) set and each set has 6 wires, namely 2 "data-in" wires, 2 "data-out" wires and the usual T and R wires. Adding or subtracting a party requires pushing a special +/- button and then a button associated with the line to be added or subtracted.
The conference bridge system according to the present invention utilizes ordinary Touch Tone (trade mark) telephones and is simpler than the system of Canadian Pat. No. 1,093,194; it does not, however, provide the same features as the system described in the patent.
Canadian Pat. No. 791,228 of Gaunt, Jr., issued July 30, 1968, discloses telephone conferencing circuits employing a series of stages arranged in a loop. Each stage includes an amplifying element, e.g. a transistor. The arrangement provides an adequate signal transmission level between the various lines and at the same time prevents regenerative circulation of signals. The patent is concerned with bridge circuits per se and does not disclose a complete system including microcomputer control such as used by the present invention.